Guy have an interesting problem here se if anyone has had the dame type issue:
My 2004 LS with 125,00 on the odo has the Trac light and check engine light come on ONLY whe nthe cars fule tank is full... Once I get down to a half tank the light resets after a restart.. weird..

The service guy says is the rear cat throwing the code.

I diont want ti just start replacing stuff and then get the codes again...

Whats throwing me off is thats itys tied to the fuel level...

Anyone else have similar ..

 

What's the exact code? 420 / 430 are post cat O2 sensors and are usually related to the cats or an exhaust leak. Your problem sounds odd. A bad pre cat O2 sensor will throw the trac light I believe.

 

thanks
....i wrote down the code.....now i can't find it ...lol

 

When the code comes back hit up an auto parts store for a free read if you can't find it.

 

I got one and now I can monitor my cat voltage as I drive on my android phone.

There are a lot of diagnostic data to be had.


I won't go into all the details but I was able to tell by the voltage differences that I was running rich on the right side. A VERY small vacuum leak was responsible. My mileage went up about 3 mpg after I fixed the faulty hose. AND, it had a lot more power!

If you put your smart hat on, this little jewel can really pay for it's self.